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least two feet tall, no offsite stormwater will enter the site. In some areas,ponding will occur <br /> against the berms, but this is unavoidable due to the rolling natural topography. <br /> Map G-1 shows the drainage area for the disturbed ground within the affected area,the runoff <br /> generated, and the capacity of stormwater control measures. The SCMs are designed around the <br /> 10-YR event, as it is a temporary condition. Once mining and reclamation is complete,the site <br /> will be revegetated for permanent runoff conditions. <br /> 2.1.1 Active Mining Area <br /> The disturbed area consists of one drainage basin. It contains all mining activity at the Hayden <br /> Gravel Pit. All of it drains to the sediment ponds identified on Map G. Upon reclamation,this <br /> area will be hay meadow and dryland pasture, the sediment pond removed, and the pre-mine <br /> drainage direction of roughly north, re-established. <br /> Since the mining activity is temporary in nature and stormwater control measures will be <br /> maintained by the operator throughout the mine life, the 10-YR event (1.60 inches) is used to <br /> size control measures. Runoff values and storage capacity can be seen on Map G. <br /> 2.1.2 Scale House and Parking Area <br /> The disturbed area consists of one drainage basin. It contains parking area associated with the <br /> truck scale and scale house. Stormwater barriers will be used on the uphill side to prevent runoff <br /> from the existing Routt County Gravel Pit from entering this area. These barriers will be <br /> constructed to the minimum dimensions as shown on Map G. The drainage basin for this area <br /> includes a portion of the hillside to the north as well as the disturbed ground. <br /> The 100-YR event (2.60 inches) is used to size control measures. Runoff values and storage <br /> capacity can be seen on Map G. <br /> 3. Groundwater <br /> Since the test pits did not show groundwater and there are no visible seeps or springs, <br /> groundwater is not expected to be encountered during mining. While no groundwater is <br /> Hayden Gravel Pit G-2 CM 1, icw,aa Asmwiatcs.ri_u <br /> May 2020 - <br />